Process of producing steel free from protoxids.



UNITED STATES PATENT OFFICE: 1 A

o'r'ro THALLNER, or nrsmnncxnfi'rrn, GERMANY, ASSIGNOR TO THE FIRM :ZF

' BIs nncKHti'r'rE, or BIsMARcKHijT'rE, GERMANY.

rnocnss or rnonucnve STEEL-FREE rnom rno'roxrns.

No Drawing.

To all whom it may concern: 1 Belt known that I, O'i'ro' THAL 'NER,met.-

- allurgist, a subject of the King of Prussia,

and resident of Bismarckhiitte, in the Provinceof Upper Silesia, GermanEmpire, have invented a new and useful Process for Producing Steel Freefrom Protoxid's, of which the following isa specification.

'- This invention relates to a process for producing steel free fromprotoxids of iron or manganese and which has the acid propertiesofcrucible steel, 1

.It is already known to apply silicon for .the deoxidation of steel andslag. In-de- -ametal that. it is not capable of separating out in theshort time before pouring. The result. s that onlya small quantity ofthe purev silicon remains in solution in the steel and as this smallquantity'only acts for a short time it has practically no influence onthe mternal structure of the-steel. :On the contrary the fine emulsifiedsilicic acid has a disadvantageous action on the internal structure. Ifit is desired to cause-the silicon to act advantageously on the internalstructure the metal .must contain a greater quantity of the silicon andbe subjected to the protracted action of the silicon at the meltingtemperature." It is known that in the Martin furnace a strong blowingaction is obtained in consequence of the gases of combustion, that is tosay, there is a constant excess of oxygen present inthe slag and thisoxygen has a constant blowin action on the metal bath below it. It is teref ore impossible to obtain a constant percentage of carbon in themetal in a basic lined furnace of this kind as the carbon in contactwith the slag which is rich in oxygen is subjected to constant changesasalso 18 the manganese in the metal bath. This oxygen of course alsoafiects the silicon as the silicon has a great affinity for the oxygen1n the slag, and passes over into,the slag as silicic acid. It appearstherefore to be unpossible to retain pure silicon dissolvedSpecification of Letters Patent.

Application filed April 20,

Patented Oct. 19, 1909.

1909 Serial No. 491,104.

pears also impossible to obtain afavorable.

ture of the steel. There still remains the possibility-of adding thesilicon before tapping or in the ladle. Silicon of course always out ofthe. slag in a Martin furnace. The object aimed at however was diflicultto obtain as the metal below the slag might still remain rich in oxygenand in addition very large quantities of silicon were necessary to slagconstantly took up oxygen from the combustion gases and this oxygen hadto be continuously removed. The slag was'therefore always more acid inits nature and increased in 'its tendency to give up oxygen to Y themetal bath. It may therefore be as sumed as a practical impossibility tomelt metal in a basic flame-heated furnace and still retain a reasonableproportion of silicon in solution.

I have discovered that the protoxids may be removed and pure silicontaken up in soan electric furnace with a basic lining and heating thesteel together with siliconin said lining in consequence of thehightemperatures obtained retains the slag in a much more basiccharacter than was at all possible in a Martin furnace. The consequenceis that the slagis lem liable to take u oxygen. from the air as there isno oxidi mg flame present in the electric furnace. The proof of metalmay be heated for several hours in an electric furnace with a basiclining without altering the percentage of carbon and manseen in that theslag may be retained free of iron for several hours. This circumstancealone permits the carrying out ofthe following process.

from any other blowing apparatus 15 passed into a basic electricfurnace. Suflicient ferrosilicon is added either in the electric furnaceor when tapping into the ladle to completely deoxidiz'e the metal and sothat a fixed amount of pure silicon remains in solution. When added.inthe electric-furnace the ferrosilicon may be laid in the furnace bringabout the permanent silicizing as the.

this may be found in the fact that the The Martin I steelorthe meltedproduct and. the metal poured thereon or the ferro with a basic linedMartin furnace and it apaction of the silicon on the internal struc- Yreduces the protoxid of iron and manganese v .80 lution by the steel bytreating blown steel in furnace. The electric furnace with a basicganese in the metal. The proof is also to be 1 addition of silicon on abasic Martin furnace v sible to add part of'the silicon to the metalbefore passing the ,same in the electric furnace and the other partafter. The chemical action which results, is as'follows: The

product of the deoxidation which is emulsified 1D. the metal has timeduring the melting in the electric furnace to separate out and" thisproduct passes in the form of silicic acid into the slag. The puresilicon held in solution ,is neutral as regards the basiclining. Inconsequence the basic lining of the furnace is not attacked whereas theexcessive led to the formation of large quantities of I silicic acidwhich attacked the lining of the furnace very severely. If the. slag inthe electric furnace still contains iron-protoxid, the iron in the slagis gradually extracted by means of the silicon in the bath and thisreduction takes place at the contact surface between the slag and themetal bath. The reduction further takes place until the whole content ofsilicon has been used up or until the slag is free of iron. vIn order toretard theloss of silicon it isnecessary to accelerate the deoxidationof"the'slag. This maybe effected by throwing on charcoal or the like oraluminium compounds or even pulverized ferrosilic'on. It isto bementioned that. a part of the deoxidizing agent burns with the airwhilethe deoxidizing means which act on the slag from below act withoutloss.

When thedeoxidation iscomplete in the slag, it becomes white or falls toa powder when exposed to the cooling action of the air. When.

the slag becomes white or falls to apowder k 40 in the air, the metalbath below the slag may Witnesses:

beassumed as in a proper state is; taking up pure silicon, and that thesilicon remaining in solution in the metal will no longer be used up. Inconsequence if further additions of ferrosilicon are made, the siliconacts on the internal structure of the metal upward that is to say fromthe metal bath upward, is also an important feature of the r metallurgicaction.

I claim l. The process of producing steel free from protoxids,consisting in blowing the steel and. passing it to a basic electricfurnace, adding silicon to said steel and heating said metal in saidfurnace together with the silicon till the metal and slagare'deoxidized. 2. The process of producing steel free from protoxids,consisting in blowing the steel and passing the blown steel to a basicelectric furnace, adding silicon to said steel, heating said metalin'said furnace-together with the silicon till the metal and slag aredeoxidized, and then adding further silicon.

3 In witness whereof I have hereunto set my hand in the presence of twowitnesses.

OTTO THALLNER.

HERMAN PLISOHKE, MAX ZIEncHE.

